Solar EUV Irradiance Variability Reflected in the Terrestrial Dayglow

ecent period from 2002 to 2008 when decreasing solar irradiance during the descending phase of the 11-
year cycle countered much of the anthropogenic warming.
According to our projections of annual mean regional surface temperature changes, shown in Figure
3, the increase from 2009 to 2014 will be largest from 30 to ∼70 o N, especially over land but also over the
ocean, except in the north east Pacific. As solar irradiance decreases and global surface temperatures
increase minimally between 2014 and 2019, the anthropogenic influence nevertheless will continue to
warm the Northern mid latitudes, but less uniformly and at a slower rate because of cooling in those
regions most sensitive to solar variability (Figure 3, bottom). Our projections are consistent with IPCC’s
long-range forecast that warming will be greatest over land and at most high northern latitudes. But
whereas IPCC asserts minimal warming in parts of the North Atlantic Ocean, our forecast suggests that
this region will warm throughout the next decade, in response to both solar and anthropogenic influences.
A major volcanic eruption or a super ENSO will modify significantly the temperature change
scenarios in Figure 3, both globally and regionally, as shown in Figure 4. A large volcanic eruption with
peak climate impact in 2014 will cool much of the Americas and the mid Atlantic Ocean, parts of
Australia, the tropical Pacific Ocean and the western India Ocean relative to the base period (1951-1980).
A “super” El Nino peaking in 2019 would produce significant warming over many regions of the globe,
as shown in Figure 4. Such a combination of an ENSO event following a Pinatubo-like eruption would
mean that rather than remaining approximately level from 2014 to 2019, global surface temperatures
would increase 0.4±0.02 o C (Figure 1), but from entirely natural (not anthropogenic) causes. A similar
sequence occurred in the recent past from mid 1992 to mid 1997, when global surface temperatures
increased 0.5 o C, significantly more than the 0.1 o C, attributable to anthropogenic warming over this
period.
4. Summary
By representing monthly mean surface temperatures in terms of their combined linear responses to
ENSO, volcanic and solar activity and anthropogenic influences, we account for 76% of the variance
observed since 1980 (and since 1889, Lean and Rind, 2008) and forecast global and regional temperatures
6